It has been used for many years to dye the hair of humans to cover appearing grey hair. The need to do so arises from the fact that grey hair is the first sign of having past adolescence, which can be hard to accept for many people.
Further, during the last few decades hair dyeing has become more and more popular in the western world. At first Punk Rockers and other society critical groups dyed their hair in extreme colors as a part of their protest against the established society, but today especially many young people also use hair dyes (in more soft tints than the Punk Rockers) as a sort of "cosmetic" to change or freshen up their "looks".
Hair Dyes
In general hair dyeing compositions on the market today can be divided into three main groups:
temporary hair dyes, PA1 semi-permanent hair dyes, and PA1 permanent oxidative hair dyes. PA1 1) one or more oxidation enzymes derived from a strain of the genus Pyricularia, PA1 2) one or more dye precursors, and optionally PA1 3) one or more modifiers.
The temporary hair dyes are only intended to change the natural hair color for a short period of time and usually function by depositing dyes on the surface of the hair. Such hair dyes are easy to remove with normal shampooing.
When using semi-permanent hair dyes the color of the dyed hair can survive for five or more shampooings. This is achieved by using dyes which have a high affinity for hair keratin and which are capable of penetrating into the interior of the hair shaft.
Permanent hair dyes are very durable to sunlight, shampooing and other hair treatments and need only to be refreshed once a month as new hair grows out. With such dyeing systems the dyes are created directly in and on the hair. Small aromatic colourless dye precursors (e.g. p-phenylenediamine and o-aminophenol) penetrate deep into the hair, where said dye precursors are oxidized by an oxidizing agent into coloured polymeric compounds. These coloured compounds are larger than the dye precursors and cannot be washed out of the hair.
By including compounds referred to as modifiers (or couplers) in the hair dyeing composition a number of hair color tints can be obtained. Cathecol and Resorcinol are examples of such modifiers.
Traditionally H.sub.2 O.sub.2 is used as the oxidizing agent (color builder) . As H.sub.2 O.sub.2 is also a bleaching agent dyeing compositions comprising H.sub.2 O.sub.2 are often referred to as "lightening dyes".
The use of H.sub.2 O.sub.2 in dye compositions has some disadvantages, as H.sub.2 O.sub.2 damages the hair. Further, oxidative dyeing usually demands high pH (normally around pH 9-10), which inflicts damage on the hair and irritate the scalp. Consequently, when using dye compositions comprising H.sub.2 O.sub.2, it is recommendable not to dye the hair often.
To overcome the disadvantages of using H.sub.2 O.sub.2 it has been suggested to use oxidation enzymes to replace H.sub.2 O.sub.2.
U.S. Pat. No. 3,251,742 (Revlon) describes a method for dyeing human hair by dye formation in situ (i.e. on the hair). An oxidative enzyme is used to the color formation reactions at a substantially neutral pH (pH 7-8.5). Laccases, tyrosinases, polyphenolases and catacolases are mentioned as the suitable oxidation enzymes.
EP patent no. 504.005 (Perma S.A.) concerns a composition for dyeing hair which do not require the presence of H.sub.2 O.sub.2 (hydrogen peroxide). Said composition comprises an enzyme capable of catalyzing the formation of polymeric dyes, and also dye precursors, such as bases and couplers, in a buffer solution. The pH in said composition lies between 6.5 and 8 and said enzyme has an optimal activity in the pH range between 6.5 and 8.
Rhizoctonia praticola laccase and Rhus vernicifera laccase have a pH-optimum between 6.5 and 8 and can be used to form the polymeric dyes according to this patent.
WO 95/33836 (Novo Nordisk A/S) describes the use of a laccase derived from Myceliopthora thermophila which may be used for dyeing of hair.
WO 96/00290 (Novo Nordisk A/S) discloses the use of a laccase derived from Polyporus pinsitus for oxidative dyeing of hair.
It is known that Pyricularia oryzae laccase may be used oxidation of phenolic azo dyes (see Muralikrishna et al., (1995), Appl. Environ. Microbiol., 61, (12), pp. 4374-4377).
The use of Pyricularia laccase for dyeing keratinous materials such as hair is not mentioned and anticipated by said document.